Moraxella bovis is a Gram-negative gammaproteobacterium and is one of the causative agents of infectious bovine keratoconjunctivitis. The structure of lipooligosaccharide (LOS) from strain Epp63 was recently elucidated. In the present study a genetic locus of seven encoding genes with high similarity to glycosyltransferases has been identified. Mutation of these putative glycosyltransferase genes resulted in M. bovis mutant bacteria that expressed truncated LOS structures. The structures of the oligosaccharide (OS) expressed by the mutant strains were elucidated and demonstrated the role of the glycosyltransferase enzymes in the LOS biosynthesis of M. bovis. The glycosyltransferase genes designated lgt1, lgt3, and lgt6 are highly similar to the genes in the related bacterium M. catarrhalis. In addition, there are syntenic similarities with the corresponding LOS biosynthesis locus in M. catarrhalis and other members of Moraxellaceae.